1. Field of the Invention
The present invention relates to methods of fabricating integrated circuit capacitors, and more particularly, to methods of fabricating integrated circuit capacitors having a cylindrical-shaped lower electrodes.
2. Description of the Related Art
As the integration density of integrated circuit and/or semiconductor memory devices increases, the devices may be scaled-down, and as such, the area of a unit memory cell in a memory device may also be reduced. However, even though a capacitor in a memory cell of a dynamic random access memory (DRAM) device may be reduced in size, a minimum capacitance may be required to provide the desired input, output, and/or data reproduction characteristics, which may seriously affect the design of memory cell capacitors. In order to fabricate capacitors to meet minimum capacitance requirements even at reduced sizes, various structures for capacitor lower electrodes, such as relatively tall and/or three dimensional structures, have been proposed. For example, a cylindrical-shaped lower electrode may offer advantages by increasing the effective area of a capacitor. As such, various cylindrical-shaped lower electrode structures and formation methods have been proposed, such as those described in U.S. Pat. No. 6,653,186 to Won et al.
Generally, in order to form a cylindrical-shaped lower electrode, a silicon nitride etch stop layer and a mold oxide layer may be formed on a semiconductor substrate including a buried contact plug therein. The mold oxide layer and the etch stop layer may be sequentially dry-etched to form a mold oxide pattern and an etch stop pattern exposing the buried contact plug. Then, using the mold oxide pattern, the cylindrical-shaped lower electrode may be formed on the contact plug and on sidewalls of the mold oxide pattern. After the lower electrode is formed, the mold oxide pattern may be removed by a wet etch.
However, in conventional methods of forming cylindrical-shaped lower electrodes, the etchant used to remove the mold oxide pattern may flow into the interface between the lower electrode and the etch stop layer, and may thereby damage the lower structure.
More particularly, where a titanium nitride (TiN) cylindrical-shaped lower electrode is formed on a polysilicon contact plug, it is known to form a Ti layer on the contact plug and silicide the Ti layer to form a TiSi2 layer on the contact plug before depositing the TiN for the lower electrode. This may decrease interface resistance between the TiN of the lower electrode and the polysilicon layer of the contact plug. However, as the entire Ti layer may not be silicided, a portion of the Ti layer may remain between the lower electrode and the etch stop layer. As such, the remaining Ti layer may be etched when the mold oxide pattern is removed after forming the lower electrode, and the etchant may flow between the lower electrode and the etch stop layer. As a result, the polysilicon contact plug in the interlayer insulating layer may be etched, which may result in defects.